1. Field of the Invention
The present invention relates to a method of measuring radiation for a radiation measurement device with at least two Geiger-Muller counter tubes of different sensitivity, high voltage supply means in connection with each of said Geiger-Muller counter tubes and microprocessor means including program storage means and random access memory means capable of switching between said Geiger-Muller tubes based on said radiation intensity whereby at least one Geiger-Muller counter tube generates pulses wherein an actual integration interval is determined by a measurement algorithm.
2. Description of Prior Art
Various radiation measuring devices, both stationary and portable, are known, including those employing a Geiger-Muller counter. In Geiger-Muller counters, a gas filled chamber is employed in which is incorporated two electrodes. The ionization produced by radiation dissipates part of all of its energy by generating electron ion pairs. A count is registered each time a pulse of voltage exceeds a minimum value established. European Patent Publication No. 0 151 880 refers to a particular radiation detector using Geiger-Muller tubes, in which instead of counting radiation pulses the elapsed time interval to the incident of the first strike is determined. This is done to avoid negative influences of dead time and thus to provide a linear read-out. Furthermore, this document discloses the possibility of switching between two different detectors based on the radiation intensity. IEEE Transactions on Nuclear Science, Vol. NS-34, No. 1, Feb. 1987 (New York, NY, U.S.A); H. C. Staley et al.: "Radiation Detection Algorithm for a Portable Survey Instrument", pp. 619 -621, discloses detectors counting impulses over a predetermined time interval.
Heretofore, different measurement instrument devices were required for different types of radiation and different intensity levels. For example, a device for measuring low level environmental background radiation would not be suitable for measuring high dose rates.